Distortion "masking" in monitors?

[CCash]

Here is the path:
ProTools > digital to Yamaha 02R > Envision DA converters > Otari Pic Mix > Apogee 3 way monitors.

I needed a quick and easy de-esser last night. I don't like the Digidesign de-esser, but I gave it a shot. Later, to double-check the mix, I sent it to another room via the 888 analog outs.

I was horrified when I heard distortion all over the dialog. I went back into the other room and plugged headphones into the 02R. Again, I heard the distortion loud and clear. Bypassing the de-esser confirmed that it was the cause of the distortion. It was intereseting that the distortion was very apparent in the headphones at low volumes, but seemed to dissappear as I turned them up.

I had a few people listen to this today just to make sure I wasn't nuts, and they were pretty surprised. Regarding the headphone volume, the only theory we could come up with is that it must a physical, human-ear phenomenem, where distortion is less apparent at higher SPLs. Anyone ever heard of this?

As for why we couldn't easily hear the distortion out of the Apogee monitors, a tech engineer took a stab at it. The dialog was very peaky in the high mids. Obviously the de-esser couldn't handle it well at the given threshhold. He thinks that perhaps because the D/A converters in the Envision that feed the Apogee monitors are superior to the converters of the 888 and the 02R's headphone section, the Envision could handle converting this signal without crapping out.

If anyone could shed some light on this I'd really appreciate it? All theories welcome.

Thanks,
Curt

[Dead Space]

As far as the volume thing goes, yes that's pretty much the deal. Your auditory system has limits to how linear it is, just like a mic preamp.

Listening at louder volumes makes it harder to hear distortion because your ears are distorting as well. Because you've heard the world this way since birth, it doesn't really register as distortion, and the non-ear generated distortion in the signal you're listening to blends in with the natural distortion of your ear.

I usually mix at moderate volumes for this and other reasons. Listen lower to hear more.